Last night a man aged 20 and two youths aged 17 were arrested by officers investigating an alleged arson attack at the Buckinghamshire home of Germaine Lindsay early on Friday. Lindsay, 19, died in the 7 July attack on the Piccadilly line train at King's Cross, which killed 26 people.

The latest attack follows an increase in racist incidents being investigated since the 7 July bombings. Five mosques and two Sikh temples across the country have been targeted by vandals in what are believed to be reprisal attacks. There has been a reported upsurge in assaults and abuse directed at Asians. Muslim leaders have appealed for calm after Thursday's attacks, but some warned the Government that it needed to revise British foreign policy if it wanted to end the threat of terrorism.

The East London Mosque and the adjoining London Muslim Centre were evacuated yesterday after a hoax bomb threat. More than 100 worshippers and schoolchildren fled the buildings, but returned after police gave the all-clear.

Police were last night investigating an arson attack on a shop opposite a mosque in Leeds. The KPS Pound Shop in Hare Hills Lane was rumoured to have been set alight by three white youths, although a spokesman for West Yorkshire Police said "there are no community tensions in the area at this time".

Azzam Tamimi, from the Muslim Association of Britain, said the country was in real danger and this would continue so long as British forces remained in Iraq. He described the 7 July bombings and the attempted attacks on Thursday as "horrifying" but said it was not enough to simply unite in condemnation.

Speaking after a Sky News debate in Birmingham, he said: "The latest developments clearly show this is a big thing. It's not just a few individuals from Leeds. It's time everybody engaged in an attempt to prevent it. Tony Blair has to listen to what the experts have been saying, that our involvement in Iraq is stupid."